Qatadah narrates from Sayyiduna Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) performed the aqiqah on behalf of Hasan and Husayn (may Allah be pleased with them both) with two rams.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19268